comparison of select analytes in aerosol from e cigarettes with smoke from conventional cigarettes and with ambient air

Methods overview ISO 17025 accredited analytical methods were used to evaluate the cigarette samples for select HPHCs in mainstream smoke.. Smoke and aerosol collection Cigarette prepara

Comparison of select analytes in aerosol from e-cigarettes with smoke

from conventional cigarettes and with ambient air

Lorillard Tobacco Company, PO Box 21688, Greensboro, NC, USA

a r t i c l e i n f o

Article history:

Received 31 July 2014

Available online xxxx

Keywords:

Electronic cigarette

Smoking

Tobacco

Nicotine

Harmful and potentially harmful

constituents (HPHC)

a b s t r a c t

Leading commercial electronic cigarettes were tested to determine bulk composition The e-cigarettes and conventional cigarettes were evaluated using machine-puffing to compare nicotine delivery and rel-ative yields of chemical constituents The e-liquids tested were found to contain humectants, glycerin and/or propylene glycol, (P75% content); water (<20%); nicotine (approximately 2%); and flavor (<10%) The aerosol collected mass (ACM) of the e-cigarette samples was similar in composition to the e-liquids Aerosol nicotine for the e-cigarette samples was 85% lower than nicotine yield for the conven-tional cigarettes Analysis of the smoke from convenconven-tional cigarettes showed that the mainstream ciga-rette smoke delivered approximately 1500 times more harmful and potentially harmful constituents (HPHCs) tested when compared to e-cigarette aerosol or to puffing room air The deliveries of HPHCs tested for these e-cigarette products were similar to the study air blanks rather than to deliveries from conventional cigarettes; no significant contribution of cigarette smoke HPHCs from any of the compound classes tested was found for the e-cigarettes Thus, the results of this study support previous researchers’ discussion of e-cigarette products’ potential for reduced exposure compared to cigarette smoke

Ó 2014 The Authors Published by Elsevier Inc This is an open access article under the CC BY license (http://

creativecommons.org/licenses/by/3.0/)

1 Introduction

Electronic cigarettes (e-cigarettes) are a relatively new

con-sumer product Unlike conventional cigarettes, e-cigarettes do

not burn tobacco to deliver flavor Instead, they contain a

liquid-based flavorant (typically referred to as e-liquid or e-juice) that

is thermally vaporized by an electric element This liquid typically

consists of a mixture of water, glycerin, and/or propylene glycol

The liquid also contains nicotine and flavor, although nicotine-free

products are available

While there are decades of characterization studies and

numer-ous standardized analytical procedures for conventional cigarettes,

relatively little published analytical data exists for commercial e-cigarette products Furthermore, no standardized test methods or reference products exist for e-cigarettes

Electronic cigarettes are generally purported to provide reduced exposure to conventional cigarettes’ chemical constituents because they deliver flavors and nicotine through vaporization rather than

by burning tobacco.Goniewicz et al (2014)reported low levels of select chemical constituents in select e-cigarette brands commer-cially available in Poland A recent review of analyses from diverse e-cigarettes shows comparatively simple chemical composition relative to conventional cigarette smoke (Burstyn, 2014) However, limited published results exist for commercial products that repre-sent a significant presence in the marketplace (Cheng, 2014) The purpose of this study was to evaluate e-cigarette products with a significant presence in the marketplace for bulk composition, including nicotine, and for select constituents for comparison with conventional cigarette products Three blu eCigs products (approx-imately 50% of the US market) and two SKYCIG products (approxi-mately 30% of the UK market) were chosen for evaluation Marlboro Gold Box (US), and Lambert & Butler Original and Menthol products (UK), with significant market share in their respective geo-graphical areas, were included in the study for conventional ciga-rette comparisons

http://dx.doi.org/10.1016/j.yrtph.2014.10.010

0273-2300/Ó 2014 The Authors Published by Elsevier Inc.

This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/3.0/ ).

Abbreviations: ACM, aerosol collected mass; HPHC, harmful and potentially

harmful constituents; CO, carbon monoxide; TSNA, tobacco-specific nitrosamines;

PAA, polyaromatic amines; PAH, polyaromatic hydrocarbons; LOQ, limit of

quan-titation; LOD, limit of detection; CAN, Health Canada Test Method T-115; blu CTD,

Classic Tobacco Disposable; blu MMD, Magnificent Menthol Disposable; blu CCH,

Cherry Crush, Premium, High Strength; SKYCIG CTB, Classic Tobacco Bold; SKYCIG

CMB, Crown Menthol Bold; MGB, Marlboro Gold Box; L&B O, Lambert & Butler

Original; L&B M, Lambert & Butler Menthol; TPM, total particulate matter; PG,

propylene glycol.

⇑ Corresponding author Fax: +1 336 335 6640.

E-mail address: rtayyarah@lortobco.com (R Tayyarah).

Contents lists available atScienceDirect

Regulatory Toxicology and Pharmacology

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / y r t p h

The products used in the study were evaluated for content and

delivery of major ingredients (glycerin, propylene glycol, water,

and nicotine) and for select constituents (carbon monoxide (CO),

carbonyls, phenolics, volatile organic compounds (volatiles),

met-als, tobacco-specific nitrosamines (TSNAs), polyaromatic amines

(PAAs), and polyaromatic hydrocarbons (PAHs)) Many of these

constituents are included in cigarette industry guidance issued

by the FDA that includes reporting obligations for harmful and

potentially harmful constituents (HPHCs) in cigarette filler and

smoke under section 904(a)(3) of the 2009 Family Smoking

Pre-vention and Tobacco Control Act (FDA, 2012) For delivery studies,

the conventional cigarettes were smoked under an intense puffing

regime published byHealth Canada (1999) The e-cigarettes were

tested using minimal modifications to this smoking regime

Ninety-nine puffs were used to collect approximately the same

aerosol mass as obtained from conventional cigarette testing

Ambient ‘air’ samples, empty port collections, were included as a

negative control of aerosol testing for cigarette constituents (i.e

HPHC)

2 Materials and methods

2.1 Test products

Two disposable cigarette products and three rechargeable

e-cigarette products were obtained from the manufacturers Three

conventional cigarette products were purchased through

whole-sale or retail sources for testing Information for each of the

prod-ucts is listed inTable 1

2.2 Methods overview

ISO 17025 accredited analytical methods were used to evaluate

the cigarette samples for select HPHCs in mainstream smoke

Offi-cial methods are cited and other, internally validated, methods are

briefly described for general understanding Furthermore, because

no standardized methods exist for e-cigarette analysis, the

meth-ods used to evaluate the conventional cigarettes were adapted to

evaluate the e-cigarette products and the study blanks (room

air) In an effort to maximize signal and lower methods’ limits of

quantitation, aerosol collection amounts were maximized (but

maintained below breakthrough) and extraction solvent volumes

were minimized In some cases, alternative instrumentation was

employed to improve detection For example, mainstream smoke

TSNAs were analyzed by GC–TEA while aerosol and air blank

sam-ples were analyzed by LC–MS/MS Accuracy, precision, and method

limits of quantitation and detection (LOQ and LOD) were verified

for each method On average, accuracy and method variability for

the analytes tested were determined to be 98% and 3%,

respec-tively Analyte LOD and LOQ information is listed inSupplemental

Appendix A Tables 1 and 2 Method resolution for low levels of

analytes was influenced by background levels of select analytes

in air control samples These background levels are attributed to

instrument or smoking machine carry-over as evidenced in solvent

or air blanks In addition, the high concentration of glycerin and water in e-cigarette aerosol present challenges for volatile-based measurement systems (i.e GC) Additional method refinements and dedicated e-cigarette puffing machines are two areas for con-sideration to improve e-cigarette aerosol method sensitivities Method development and verification details for e-cigarette liquids and aerosols are the subject of a future publication

2.3 Smoke and aerosol collection Cigarette preparation and machine smoking for conventional cigarettes are described in Health Canada Test Method T-115 (CAN) (1999) Two to three cigarettes were smoked per replicate for conventional cigarettes and 99 puffs were taken from single e-cigarettes for no more than approximately 200 mg of particu-lates collected per pad Three to five replicates were tested for each measurement Prior to analysis, filter pads from cigarette smoke collection were visually inspected for overloading of particulates,

as evidenced by brown spotting on the back of the filter pad To ensure no overloading of particulates for aerosol collection, e-ciga-rette units were weighed before and after collection to verify that product weight change and filter pad weight change were compa-rable Air blanks were prepared by puffing room air (99 puffs) through an empty smoking machine port to the indicated trapping media for an analysis method These air blank samples were pre-pared and analyzed in the same manner and at the same time as the e-cigarette aerosol samples Smoke and aerosol collection sec-tions were conducted separately Smoke and aerosol particulate was collected onto 44 mm glass fiber filter pads with >99% partic-ulate trapping efficiency for each replicate analysis For carbonyls, smoke/aerosol was collected directly by two impingers, in series For smoke metals analysis, electrostatic precipitation was used For volatiles and PAH determinations, single chilled impingers were placed in-line with the filter pads e-Liquid glycerin and nic-otine were quantitated using GC–FID and/or GC–MS using a method equivalent to ISO 10315 (ISO, 2000a) e-Liquid water was quantitated using Karl Fischer analysis A reference e-liquid was developed and used as a testing monitor for ingredient determina-tions in the e-liquid samples The reference e-liquid is composed primarily of glycerin, propylene glycol, and water with low levels

of nicotine, menthol, and Tween 80 The Tween 80 is added to improve solubility of menthol in the solution The reference is not meant to directly mimic an e-liquid used for consumption but merely used for analytical control charts Three replicates were tested for each sample and the reference

2.4 Analytical assays Carbon monoxide was determined concurrently with aerosol and smoke collection for nicotine and water and analyzed by NDIR using ISO method 8454:2007 (ISO, 2007) Carbonyls were trapped using 2,4-dinitrophenylhydrazine as a derivatizing agent with

Table 1

List of cigarette and e-cigarette products tested.

Classic Tobacco Disposable (blu CTD) blu eCigs Disposable e-cigarette Content: 24 mg/unit

Magnificent Menthol Disposable (blu MMD) blu eCigs Disposable e-cigarette Content: 24 mg/unit

Cherry Crush, Premium, High Strength (blu CCH) blu eCigs Rechargeable e-cigarette Content: 16 mg/unit

Lambert & Butler Original (L&B O) Imperial Tobacco Conventional cigarette Yield: 0.9 mg/cig (ISO)

Lambert & Butler Menthol (L&B M) Imperial Tobacco Conventional cigarette Yield: 0.5 mg/cig (ISO)

subsequent analysis by UPLC–UV using CORESTA method 74

(CORESTA, 2013) For phenolics determination, filter pads were

extracted with 20 mL of 1% acetic acid/2.5% methanol (MEOH) in

water using 30 min of agitation Extracts were analyzed by

UPLC-fluorescence detection using a C18 column for separation For

vol-atiles analysis, filter pads and impinger solutions (20 mL MEOH)

were combined Extracts were analyzed by GC–MS in SIM mode

using a WAX capillary column For metals analysis, cigarette smoke

was collected using an electrostatic precipitator while e-cigarette

aerosol was collected on glass fiber filter pads After smoking, the

cigarette smoke condensate was rinsed from the electrostatic

pre-cipitation tube using methanol The dried condensates were

digested using hydrochloric (10% v/v), nitric acids (80% v/v), and

heat and were diluted prior to analysis by ICP-MS For aerosol

sam-ples, filter pads were extracted using 20 mL of a mixture of nitric

(2% v/v) and hydrochloric acids (0.5% v/v) using wrist action shaker

(20 min) Resultant extracts were analyzed by ICP-MS equipped

with an octapole reaction cell

For TSNA analysis of smoke, samples were extracted in

nonpo-lar solvent, treated to an SPE clean-up, concentrated and analyzed

by GC–TEA following CORESTA method 63 (CORESTA, 2005) For

TSNA analysis of aerosol samples, filter pads were extracted with

20 mL of 5 mM aqueous ammonium with 15 min of shaking

Extracts were analyzed by LC–MS/MS with a C18 column For

PAA determinations, filter pads were extracted using 25 mL of 5%

HCl (aq) and shaking (30 min) followed by solvent exchange and

derivatization with pentafluoropropionic acid anhydride and

tri-methylamine After an SPE clean-up step (FlorisilÒSEP-PAK),

sam-ples were analyzed by GC–MS in SIM mode using negative

chemical ionization PAH analysis was conducted by extraction in

MEOH followed by SPE clean-up and analysis by GC–MS in SIM

mode (Tarrant et al., 2009)

The results obtained from these analyses were tabulated as

mean ± one standard deviation for levels of selected compounds

in Supplementary Appendix A In cases where quantifiable

amounts of analyte were present in an e-cigarette aerosol sample

above that of the associated air blanks, an Analysis of Variance

(ANOVA) was used to compare the means for the cigarette smoke

data with respective aerosol data Statistical analyses were

per-formed using JMP 10.0.0 (SAS Institute, Inc Cary, NC, USA) The

sig-nificance level was established as p < 0.05 for all comparisons

3 Results and discussion

3.1 Collection of aerosol

Machine smoking of cigarettes under standardized regimes is

for comparative purposes and is not intended to represent the

range of consumer smoking behaviors Thus, standardized equip-ment, cigarette reference products, and methodology have been established to allow comparison of different products under a com-mon set of controlled conditions ISO 3308:2000E and Health Can-ada (CAN) methods are frequently used for standardized smoking

of conventional cigarettes for the purposes of laboratory compari-sons among products (ISO, 2000b; Health Canada, 1999) Following each of these methods, conventional cigarettes are smoked to a specified butt length using a fixed and specified puffing volume, duration, and interval

Regarding e-cigarette experimentation, there is no generally accepted standard e-cigarette puffing regime at this time Topogra-phy studies are limited but anecdotal information indicates e-cig-arette usage depends greatly on the individual consumer and product design and capabilities For the purposes of this study, our objective was to collect sufficient aerosol to be able to detect,

if present, select HPHCs A wide range of parameters would be ade-quate to accomplish this Given the objectives of this study, use of collection parameters which are compatible with conventional and electronic cigarettes was essential for facilitating comparisons between cigarette smoke and e-cigarette aerosol The more intense

of the standard regimes used with cigarettes, CAN, which requires

55 mL puffs taken twice a minute, was adapted for this investiga-tion The key difference required for testing e-cigarettes with the CAN method is that a fixed puff count (rather than ‘butt length’)

is necessary for aerosol collection A standard of 99 puffs was adopted for all e-cigarette and air blank analyses This puff count provides similar total particulate collection per pad between the e-cigarette samples and the conventional cigarette testing This also represents approximately 11 times more puffs than are typi-cally observed for a conventional cigarette Marlboro Gold Box, L&B O, and L&B M averaged 9.1, 8.2, and 7.2 puffs per cigarette, respectively, when machine-smoked to the standard butt length

If more aggressive puffing parameters had been chosen for the study, the puff count specification would have been lowered to maintain the target level of ACM collected Note that the range of puffs collected in-use may vary widely depending on product design, battery strength, and user puffing preferences Thus, the

99 puffs collection in this study is not intended to represent a life time use yield for any of the analytes tested

3.2 Aerosol and smoke characterization – reference information Traditional cigarette testing incorporates the use of monitor or reference cigarettes that serve as positive controls and provide quality metrics for standardized analytical methods Key examples are Kentucky Reference cigarettes and CORESTA monitor cigarettes (CORESTA, 2009; ISO, 2003; University of Kentucky, 2014) Each of

Table 2

Percent composition of e-liquid and aerosol.

(%) e-Liquid composition

e-Cigarette aerosol composition b

a

Flavor content is estimated by difference.

b

Aerosol % composition calculated based on the ACM delivery as analyte yield (mg)/ACM (mg)  100.

these reference cigarettes can serve as a single positive control and

an indicator of method variability within and among laboratories

for all analytes of interest The manufacture, design, and function

of these reference products are similar to those of commercial

cig-arettes Currently reference products are not available for

e-ciga-rette testing Given the range of e-cigae-ciga-rette designs, development

of a consensus strategy to produce positive controls or monitors

for e-cigarette testing is needed

In the absence of standardized e-cigarette references, measures

were taken to ensure experimental robustness For example,

aero-sol collected mass (ACM) results for the e-cigarette samples were

compared across methods as an indicator of puffing consistency

for a given product among the machine-puffing sessions required

to conduct the battery of tests Thus, if a sample set yielded ACM

outside of a specified ranged deemed typical for a given product,

the sample set was repeated This range was determined for each product based on collection of 20 or more replicates across the product lot using CAN parameters

Also, because results from initial analyses indicated low or no measurable levels of many of the analytes, blank samples were included to verify any contribution of analyte from the laboratory environment, sample preparation, and/or analyses for each HPHC test method The air blank results are listed with the samples’ results inTables 4 and 5 There were instances for which solvent blank and air blank samples had measurable levels of an analyte This is due to the ubiquitous nature of some of the analytes, such

as formaldehyde, or to carry-over Laugesen reported similar find-ings (2009) These observations serve as a cautionary note regard-ing the measurement of extremely low levels of constituents with highly sensitive instrumentation

3.3 Main ingredients e-Liquid expressed from the individual products was tested for reported e-cigarette ingredients to compare the percent composi-tions of the e-liquids and the aerosols Percent composition calcu-lations of the ingredients are shown inTable 2for each sample and

inFig 1for blu CTD, as this product’s comparative results were exemplary of the samples The primary ingredients in the e-ciga-rette samples were glycerin and/or propylene glycol (P75%) Water (618%) and nicotine (2%) were also present Based on a mass balance, other ingredients, presumed to be flavorants, were present at less than 7% Note that this calculation would also include method uncertainty and any possible HPHCs, if present The composition of the aerosol was calculated based on the ACM delivery as analyte yield (mg)/ACM (mg)  100 The bulk composi-tion of the delivered aerosol was similar to the bulk composicomposi-tion of the e-liquid

By comparison, the total particulate matter (TPM) of the con-ventional cigarettes tested is 30% water and <5% nicotine The essential difference between the ACM composition of the e-ciga-rettes tested and the TPM of the conventional cigae-ciga-rettes is that the remaining 65% of the TPM of the conventional cigarette is pre-dominantly combustion byproducts There was no detectable car-bon monoxide in the emitted aerosol of the e-cigarette samples The conventional cigarettes, on the other hand, delivered more than 20 mg/cig of CO Smoke composition for Marlboro Gold Box, exemplary of the conventional cigarettes tested, is shown in Fig 1in contrast to the e-liquid and aerosol results for blu CTD While the percent composition of the nicotine in the ACM and TPM are relatively similar, it should be noted that the actual deliv-eries of nicotine are markedly lower for the e-cigarettes tested than the conventional cigarettes The nicotine yields ranged from

8lg/puff to 33lg/puff for the e-cigarette samples which was 85% lower than the 194–232lg/puff for the conventional cigarettes These results are presented inTable 3

3.4 Aerosol and smoke HPHC testing For cigarette smoke analysis, the conventional cigarettes were machine smoked by established cigarette smoking procedures Approximately 7–9 puffs per cigarette were collected For the e-cigarette samples and air blanks, 99 puffs were collected Results were compared on an ‘as tested’ basis; i.e yields for a single ciga-rette of 7–9 puffs compared to yields from 99 puffs of an e-ciga-rette as displayed in Table 4 Additionally, in order to simplify making comparisons between the cigarette and e-cigarette sam-ples, all values were converted to yield per puff These results are summarized by class inTable 5 Results for individual analytes are tabulated as mean ± one standard deviation inSupplemental Appendix A Tables 1 and 2

Fig 1 Percent composition comparison for e-liquid, e-cigarette aerosol, and

cigarette smoke: (a) Classic Tobacco Disposable e-liquid Composition (b) Classic

Tobacco Disposable Aerosol Composition (99 puffs, CAN) (c) Marlboro Gold Box

Smoke Composition (9 puffs, CAN).

Table 3

Nicotine content and yield comparison between e-cigarettes and conventional cigarettes (mean ± standard deviation).

Nicotine content (lg/unit) Nicotine yield (lg/puff)

Number of replicates = 3–5.

Table 4

Analytical characterization of commercial e-cigarettes and conventional cigarettes collected using CAN parameters – select cigarette HPHC methodology (mg/total puffs collected) summary by analyte classes.

CO Carbonyls a

Phenolics b

Volatiles c

Metals d

TSNAs e

PAA f

PAH g

Sum

blu CTD (mg/99 puffs) <0.1 <0.07 <0.001 <0.001 <0.00004 <0.00002 <0.000004 <0.00016 <0.17 blu MMD (mg/99 puffs) <0.1 <0.08 <0.001 <0.001 <0.00004 <0.00002 <0.000004 <0.00016 <0.18 blu CCHP (mg/99 puffs) <0.1 <0.05 <0.003 <0.0004 <0.00004 <0.00002 <0.000004 <0.00014 <0.15 SKYCIG CTB (mg/99 puffs) <0.1 <0.06 <0.0010 <0.008 <0.00006 <0.000013 <0.000014 <0.00004 <0.17 SKYCIG CMB (mg/99 puffs) <0.1 <0.09 <0.0014 <0.008 <0.00006 <0.000030 <0.000014 <0.00004 <0.20 Air Blank (blu Set) (mg/99 puffs) <0.1 <0.06 <0.001 <0.0004 <0.00004 <0.00002 <0.000004 <0.00015 <0.16 Air Blank (SKYCIG Set) (mg/99 puffs) <0.1 <0.05 <0.0009 <0.008 <0.00006 <0.000013 <0.000014 <0.00006 <0.16

< Indicates some or all values were below method limits of quantitation or detection, number of replicates = 3–5.

a Formaldehyde, acetaldehyde, acrolein propionaldehyde, crotonaldehyde, MEK, butyraldehyde.

b

Hydroquinone, resorcinol, catechol, phenol, m-+p-cresol, o-cresol.

c

1,3-Butadiene, isoprene, acrylonitrile, benzene, toluene, styrene.

d

Beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, selenium, tin.

e

NNN, NAT, NAB, NNK.

f

1-Aminonaphthalene, 2-aminonaphthalene, 3-aminobiphenyl, 4-aminobiphenyl.

g

Naphthalene, acenaphthylene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, pyrene, benzanthracene, chrysene, benzo(b)fluoranthene, benzo(k)flu-oranthene, B(a)P, indeno[1,2,3-cd]pyrene, benzo(g,h,i)perylene.

Table 5

Analytical characterization of commercial e-cigarettes and conventional cigarettes collected using CAN parameters – select cigarette HPHC methodology (lg/puff) summary by analyte classes.

blu Classic Tobacco Disposable <1.0 <0.7 <0.01 <0.01 <0.0004 <0.0002 <0.00004 <0.002 <1.7 blu Magnificent Menthol Disposable <1.0 <0.8 <0.01 <0.01 <0.0004 <0.0002 <0.00004 <0.002 <1.8 blu Cherry Crush High Premium <1.0 <0.5 <0.03 <0.004 <0.0004 <0.0002 <0.00004 <0.001 <1.5 SKYCIG Classic Tobacco Bold <1.0 <0.6 <0.01 <0.08 <0.0006 <0.0001 <0.00014 <0.0004 <1.7 SKYCIG Crown Menthol Bold <1.0 <0.9 <0.01 <0.08 <0.0006 <0.0003 <0.00014 <0.0004 <2.0 Air Blank (blu Set) <1.0 <0.6 <0.01 <0.004 <0.0004 <0.0002 <0.00004 <0.002 <1.6 Air Blank (SKYCIG Set) <1.0 <0.5 <0.01 <0.08 <0.0006 <0.0001 <0.00014 <0.001 <1.6

< Indicates some or all values were below method limits of quantitation or detection, number of replicates = 3–5.

a

Formaldehyde, acetaldehyde, acrolein propionaldehyde, crotonaldehyde, MEK, butyraldehyde.

b

Hydroquinone, resorcinol, catechol, phenol, m-+p-cresol, o-cresol.

c

1,3-Butadiene, isoprene, acrylonitrile, benzene, toluene, styrene.

d Beryllium, cadmium, chromium, cobalt, lead, manganese, mercury, nickel, selenium, tin.

e NNN, NAT, NAB, NNK.

f 1-Aminonaphthalene, 2-aminonaphthalene, 3-aminobiphenyl, 4-aminobiphenyl.

g

Naphthalene, acenaphthylene, acenaphthene, fluorine, phenanthrene, anthracene, fluoranthene, pyrene, benzanthracene, chrysene, benzo(b)fluoranthene, benzo(k)flu-oranthene, B(a)P, indeno[1,2,3-cd]pyrene, benzo(g,h,i)perylene.

All analytes tested were present in the cigarette smoke at

quan-tifiable levels except for select metals These results are consistent

with internal historical results for commercial cigarettes tested

under the CAN smoking regime For the cigarette samples, the total

yield range was 3069–3350lg/puff of HPHCs tested

Of the 55 HPHCs tested in aerosol, 5 were quantifiable in an

e-cigarette sample but not the associated air blank The quantifiable

results for aerosol are listed inTables 6 and 7in contrast with the

conventional cigarettes from the same geographical region The

five analytes which were quantifiable were statistically different

(p < 0.05) at levels 50–900 times lower than the cigarette smoke

samples Phenol was quantified in one e-cigarette product at

900 times lower than cigarette smoke N-Nitrosoanatabine was

quantified in one product at 50 times lower than cigarette smoke

Three carbonyls (acrolein, acetaldehyde, and propionaldehyde)

were quantified at 86–544 times lower than cigarette smoke

All other analytes were not quantifiable above the air blanks in

aerosol samples The e-cigarettes and air blanks total yields for

analytes were <2lg/puff which is 99% less than the approximately

3000lg/puff quantified for the cigarette smoke samples Thus, the

results support the premise of potentially reduced exposure to

HPHCs for the e-cigarette products compared to conventional

cig-arette smoke

4 Conclusions

The purpose of this study was to determine content and

deliv-ery of e-cigarette ingredients and to compare e-cigarette aerosol

to conventional cigarettes with respect to select HPHCs for which

conventional cigarette smoke is routinely tested Routine

analyti-cal methods were adapted and verified for e-cigarette testing

Aer-osol collection was conducted using conventional smoking

machines and an intense puffing regime As machine puffing

can-not, and is not intended to, mimic human puffing, results of this

study are limited to the scope of the comparisons made between

the e-cigarette and conventional cigarette products tested

The main ingredients for the e-cigarettes tested were consistent

with disclosed ingredients: glycerin and/or propylene glycol

(P75%), water (618%), and nicotine (2%) Machine-puffing of

these products under a standardized intense regime indicated a

direct transfer of these ingredients to the aerosol while

maintain-ing an aerosol composition similar to the e-liquid Nicotine yields

to the aerosol were approximately 30lg/puff or less for the

e-cig-arette samples and were 85% lower than the approximately

200lg/puff from the conventional cigarettes tested

Testing of the e-cigarette aerosol indicates little or no detect-able levels of the HPHC constituents tested Overall the cigarettes yielded approximately 3000lg/puff of the HPHCs tested while the e-cigarettes and the air blanks yielded <2lg Small but mea-surable quantities of 5 of the 55 HPHCs tested were found in three

of the e-cigarette aerosol samples at 50–900 times lower levels than measurable in the cigarette smoke samples Overall, the deliv-eries of HPHCs tested for the e-cigarette products tested were more like the study air blanks than the deliveries for the conventional cigarettes tested Though products tested, collection parameters, and analytical methods are not in common between this study and others, the results are very consistent Researchers have reported that most or all of the HPHCs tested were not detected

or were at trace levels.Burstyn (2014)used data from approxi-mately 50 studies to estimate e-cigarette exposures compared to workplace threshold limit values (TLV) based on 150 puffs taken over 8 h The vast majority of the analytes were estimated as

1% of TLV and select carbonyls were estimated as <5% of TLV Cheng (2014)reviewed 29 publications reporting no to very low levels of select HPHCs relative to combustible cigarettes, while not-ing that some of the tested products exhibited considerable vari-ability in their composition and yield Goniewicz et al (2014) tested a range of commercial products and reported quantifiable levels for select HPHCs in e-cigarette aerosols at 9- to 450-fold lower levels than those in cigarette smoke that in some instances were on the order of levels determined for the study reference (a medicinal nicotine inhaler) Laugesen (2009) and Theophilus

et al (2014) have presented results for commercial e-cigarette product liquids and aerosols having no quantifiable levels of tested HPHCs, or extremely low levels of measurable constituents relative

to cigarette smoke Additionally, findings from several recent stud-ies indicate that short-term use of e-cigarettes by adult smokers is generally well-tolerated, with significant adverse events reported relatively rarely (Etter, 2010; Polosa et al., 2011, 2014; Caponnetto et al., 2013; Dawkins and Corcoran, 2014; Hajek

et al., 2014) Thus, the results obtained in the aforementioned stud-ies and in the present work broadly support the potential for e-cig-arette products to provide markedly reduced exposures to hazardous and potentially hazardous smoke constituents in smok-ers who use such products as an alternative to cigarettes Additional research related to e-cigarette aerosol characteriza-tion is warranted For example, continued characterizacharacteriza-tion of

Table 6

Per puff comparisons of quantifiable analytes for blu eCigs products from CAN puffing – yields and ratios to conventional product yields.

900

a Fewer than three replicates were quantifiable; no standard deviation is listed.

Table 7

Per puff comparisons of quantifiable analytes for SKYCIG products from CAN puffing – yields and ratios to conventional product yields.

L&B averagelg/puff SKYCIG CTBlg/puff SKYCIG CMBlg/puff L&B average/SKYCIG CTB L&B average/SKYCIG CMB

a

Fewer than three replicates were quantifiable; no standard deviation is listed.

major components and flavors is needed Establishment of

stan-dardized puffing regimes and reference products would greatly

aid sharing of knowledge between researchers Continued

meth-ods’ refinement may be necessary for improved accuracy for

quan-titation of analytes at the low levels determined in this study To

that end, it is critical that negative controls and steps to avoid

sam-ple contamination be included when characterizing e-cigarette

aerosol since analytes are on the order of what has been measured

in the background levels of a laboratory setting Though

research-ers have reported quantification of select analytes, great care must

be taken when interpreting results at such trace levels

Conflicts of interest

The company for which the study authors work and the

compa-nies that manufacture the e-cigarettes tested for this study are

owned by the same parent company

Acknowledgments

We thank the analytical testing laboratories at Lorillard Tobacco

Company for methods development and testing and Drs Brown,

D’Ruiz, Heck and Stevens for technical discussions

Appendix A Supplementary data

Supplementary data associated with this article can be found, in

the online version, at http://dx.doi.org/10.1016/j.yrtph.2014

10.010

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